.380 2 1/4" Rigby Express info needed

Hi All, I am looking for more information on the .380 2 1/4" Rigby Express cartridge.

  1. Is that the correct name? Or should it just be .380 Rigby, .380 Rigby Express, or .380 Rigby 2 1/4"?
  2. I have it listed as a 0.360" bullet diameter. Is that right? Why would it by named the .380 if it has a bullet diameter of .360?

Thanks!
Joel

Also, what date was it introduced?